IODP Expedition 364

IODP Expedition 364 was a landmark drilling project that recovered the first-ever core samples from the peak ring of the Chicxulub crater, the impact structure linked to the Cretaceous–Paleogene extinction event. Conducted in 2016 aboard the L/B Myrtle, the expedition was a collaboration between the International Ocean Discovery Program and the European Consortium for Ocean Research Drilling. The mission successfully drilled over 1,300 meters into the offshore portion of the crater, yielding unprecedented geological records of the catastrophic event that reshaped life on Earth.

Expedition Overview

The expedition was proposed and led by an international team of scientists, including co-chief scientists Sean P. S. Gulick from the University of Texas at Austin and Joanna V. Morgan from Imperial College London. Operations were conducted from the liftboat L/B Myrtle, which was positioned at a site approximately 30 kilometers offshore from Progreso in the Yucatán Peninsula. The project involved researchers from numerous institutions, including the University of Arizona, the University of Copenhagen, and the Japan Agency for Marine-Earth Science and Technology. Funding and logistical support were provided by the International Ocean Discovery Program and its European partner, ECORD.

Scientific Objectives

The primary goal was to test hypotheses about the formation of large impact craters, particularly the genesis of peak rings, by directly sampling the Chicxulub crater's subsurface structure. A core objective was to investigate the thermal and chemical evolution of the crater's peak ring and the processes of rapid rock weakening that allowed its formation. Scientists aimed to analyze the post-impact hydrothermal system to understand how such extreme environments could have fostered early microbial life. Furthermore, the expedition sought to recover a continuous sedimentary record from the first materials deposited after the impact, providing a high-resolution timeline of the recovery of life in the immediate aftermath of the mass extinction.

Drilling and Coring Operations

Drilling commenced at Site M0077, penetrating a water depth of about 17 meters in the Gulf of Mexico. Using a combination of advanced coring tools, the team drilled through 506 meters of post-impact Paleogene sediments, including a critical layer of suevite and impact melt rock. The borehole then entered the peak ring, ultimately reaching a total depth of 1,335 meters below the sea floor. Continuous coring with nearly 100% recovery was achieved using the MARUM-designed MeBo drilling system and other specialized equipment. The cores were immediately described and analyzed on board by a team of sedimentologists, petrologists, and geophysicists before being shipped to the IODP Gulf Coast Repository at Texas A&M University.

Key Findings and Discoveries

The cores revealed that the peak ring was composed of granite brought up from the mid-crust, fundamentally altering models of crater formation by showing these rocks were weakened temporarily by the immense forces of the impact. Analysis of the suevite and melt-rich rocks provided direct evidence of the incredible energy released, with models suggesting the impactor was a carbonaceous chondrite. Sediments deposited in the first days to years after the impact contained charcoal and biomarkers, indicating global wildfires and a subsequent microbial ecosystem that thrived in the crater's hot, mineral-rich hydrothermal system. The precise dating of the sediments above the impact breccia helped calibrate the timeline for the rapid return of marine life, including pioneering dinoflagellates and foraminifera.

Impact and Significance

The findings have profoundly influenced the fields of impact cratering, astrobiology, and paleoclimatology, providing the first ground-truth data for models of large impacts on Earth and other planetary bodies like the Moon and Mars. The expedition demonstrated that impact craters can create transient habitable niches, informing the search for life on other worlds. The detailed record of the Cretaceous–Paleogene boundary has become a global benchmark for understanding mass extinction events and planetary resilience. The success of the project has led to further proposed drilling within the Chicxulub crater and has cemented the legacy of the International Ocean Discovery Program in addressing fundamental questions in Earth and life sciences.

Category:International Ocean Discovery Program expeditions Category:Chicxulub crater Category:2016 in science